https://uxdesign.cc/human-eyes-understanding-of-space-for-augmented-reality-d5ce4d9fa37b

From an engineering standpoint, our eyes are precision optical sensors and the structure of it has long been used as a blueprint to design cameras. Light enters through a series of optical elements. Refraction and focus happens here. The diaphragm controls the amount of light passing through an aperture. The subsequent light pattern falls on an image plane from where electrical signals are sent to the brain. These signals are then decoded as images. Although the functioning of the eye is an interesting topic in itself, for the sake of simplicity, I have taken the liberty to omit a large portion of how the eye works. But I’m sure you get the general idea. What is more interesting and relevant is what this amazing organic optical sensor enables humans.

Human sight exists due to light. A form of electromagnetic radiation, light is the key stimulus for human vision. This radiation moves through space in the form of waves and is capable of stimulating the retina to produce a sense of vision. Electromagnetic radiation is classified according to it’s wavelength which is the distance between two crests of a wave. Although the the entire electromagnetic spectrum includes radio waves, infrared, x-rays and other wave types, the human eye is only sensitive to a narrow band between 380–740 nanometers. This is known as the visible spectrum.1 nanometer = billionth of 1 meter